erik.pilkington added a comment.
In D66856#1648809 <https://reviews.llvm.org/D66856#1648809>, @aaron.ballman
wrote:
> I'm wondering whether this should even warn pedantically. There are no format
> specifiers that apply directly to a `_Bool` datatype, so the user is left
> making a choice as to what specifier fits best. I think `hhd` and `hhu` are
> both equally reasonable types, as are the `d` and `u` groups directly -- I
> don't think we should warn on either of those specifiers with a `_Bool`
> argument. I could maybe see a case for pedantically diagnosing `h`, `l`, and
> `ll` prefixes with `_Bool` because that seems a bit type-confused to me. `c`
> as a specifier seems weird (given that false values will potentially
> terminate the string suddenly depending on terminal behavior, IIRC), but `lc`
> seems like type confusion again.
Hmm... on second though I think the `l` and `ll` prefixes are worth -Wformat
proper, since that can result in printing a half-initialized integer when the
argument ends up on the stack (we generate `movl $0,(%rsp)` for the first stack
argument). I think `%c` is probably also worth a -Wformat, it seems like it
would almost certainly be a mistake. I suppose we could pedantically warn on
`%hd`, but I'm not sure. Who is the audience for -Wformat-pedantic? Users that
expect it to diagnose any pedantically-UB printf calls will already be
disappointed, since the C standard seems to be quite a lot more restrictive
then us (7.21.6.9p9 says: "If any argument is not the correct type for the
corresponding conversion specification, the behavior is undefined." (I'm
assuming "correct type" means "same type")). So I think we should just concern
ourselves with calls that would lead to actual problems at runtime, or are
likely programmer errors, and `printf("%hd", (_Bool)0)` doesn't seem to meet
either of those bars.
Repository:
rC Clang
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D66856/new/
https://reviews.llvm.org/D66856
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